Here's some discussion we had on a previous forum thread:

A good trick for stellar AM reception is to recognize that AM is as Ernie says, very susceptible to interference from modern gear.

The best AM antenna is a long thick (16 gauge or better) wire positioned in a straight line grounded at the tuner. It is better for the wire to be HORIZONTAL, but you can make a vertical antenna if you have to. It is possible to isolate it from external interference by using a single coaxial cable through the house sheilding the signal from external interference and terminating to your 16 gauge antenna outdoors. This is a perfect lightning rod, so it is impractical for most custom installations. A hobbyist might be willing to disconnect the antenna and throw it out a window before a storm, but most of our customers would treat this as a license to sue. To be the most effective, a long wire antenna for AM should be tuned with a coupling circuit to "adjust" a physical 50-100 foot of antenna to "behave" like the ideal 290 to 865 feet (for broadcast band AM). If you would like info on a coupling circuit, check this article out in your local public library:

Popular Electronics, March, 1968, pp 53-55

For most custom installations the best alternative is to construct a simple loop antenna. A loop requires that you terminate both ends of the wire at the tuner. Most of the AM tuner sections we see will perform very well with a 10' vertical loop in the attic fed by two coaxs to the actual tuner (two coaxial cables to keep both ends of the loop shielded). Be careful to keep the loop VERTICAL. Horizontal loops create nulls in reception.

If you are really interested in maximizing AM reception in a compact space, you might want to build a real loop antenna that you can rotate for the best results per station. In the golden age of radio, these were available as accessories for wealthy. Check out this article in your local public library if you are interested in building one of your own:

"Low Cost Loop Antenna Extends AM Radio Reception" Douglas Kohl, Popular Electronics, July, 1978
Response by Jay In Chicago on 11/17/02 00:17

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Is that a 10' High Loop ant. in the attic?..
I immagine 10"... right?

I noticed the AM loops I've made have worked better If I ade the loops while connected to the receiver, so I could hear the cahngesa and find the perfect number of loops for a given station.

I've not heard great things about HK tuners.. am and fm.. is this true?




(15)Response by Eric Johnson on 11/17/02 10:43

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Jay,

The attic loop is a 10 foot diameter loop of one turn. If you make loops of many turns there is a formula that decries the results. A 9.7 inch square sided loop (9.7" on each side) should be 25 turns, while a 10.1" would be 24 turns.

A loop antenna like this should be constructed so that each loop is at least 1/4" away from the next loop. I've done this by notching wooden dowels mounted to a wall.

Any loop will give it's best results if it can rotate. A station that is lined up with the plane of the loop can be "nulled" out, so that you can listen to a much more distant station.

Larry,

I remember too. Hot stuff for $199!

Ernie,

I let go of mine too, just use the local library a lot.


(16)Response by Jay In Chicago on 11/17/02 16:34

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How do you keep that 10' loop reasonably round?... or don't you? also... How directional is it?


(17)Response by Eric Johnson on 11/19/02 18:17

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I've never tried to make them round, I always made them with square sides using four tie points made of wire ties attached to floor ceiling etc.

The loop will null out (weaken) a station that is on the plane of the loop. It will strengthen a station that is facing the loop.